Acute Hypoxemic Respiratory Failure (AHRF)

- severe hypoxemia that is relatively refractory to oxygen therapy
- caused by

• homogenous lung lesions, producing pulmonary oedema
• permeability or low pressure oedema (ARDS)
• oedema of unclear or mixed etiology
• non-homogenous AHRF (usually lobar bacterial pneumonia)

Adult Respiratory Distress Syndrome (ARDS)

- acute lung injury from a variety of causes
- characterized by interstitial and/or alveolar edema and hemorrhage
- as well as perivascular pulmonary edema
- associated with hyaline membrane formation, proliferation of collagen fibers, and swollen epithelium with increased pinocytosis
- may involve

• complement system
• neutrophils
• macrophage activation
• oxygen free radicals
• cytokines

- as injury progress, there might be

• hyaline membrane
• extensive necrosis of type I alveolar epithelial cells

- late / proliferative phase is characterized by

• large dead space fraction
• high airway pressures
• pulmonary hypertension
• honeycomb appearance

What is atelactasis?

Decreased or absent air in the entire or part of a lung, with resulting loss of lung volume.

Check out pulmonary collapse